journal plastic introduction

8/9/2019 journal plastic introduction

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1. Introduction

Recycling of plastic discards is one method of reducing municipal solid waste.

They are beginning to join glass, steel, aluminum and paper as waste stream components

that have been accepted into recycling programs across the country. It is difficult,

however, to expand post-consumer plastics recycling beyond the easily recognized milk

jugs and soda bottles for technical, economic and social reasons lJJ.S. EPA, 1990al:

The

vari et y of pl ast i c wast es

Plastics in municipal solid waste (MSW) are a

very heterogeneous collection of materials that encompass not only a broad

range of types made from a single resin, but also an increasing number of items

that include a blend of resins, either mechanically or chemically bonded

together. The varieties are made additionally diverse through the use of plastic

additives to yield specific product qualities.

* The

dif i ctdt y of sort i ng plasti c resi ns

It is technically difficult to obtain

relatively pure resins from mixed plastics collected for recycling. Commercially

demonstrated separation technologies are almost exclusively limited to

processes that separate polyethylene terephthalate (PET) and high density

polyethylene (HDPE).

.

Low densi t y of post consumer pl ast i cs w astes

Plastics occupy a high

volume/weight ratio compared to other recyclable constituents in MSW, and this

adversely affects the practicality and economics of plastics collection in a

recycling program. Landfill diversion rates are measured on a weight basis and

the weight conuibution of plastics to MSW is relatively small (even though the

landfill volume occupied by plastics is large). The large volume occupied by

plastics in a recycling truck can displace the ability to collect other “heavier”

recyclables.

Li mi t ed histor y of plasti cs recycli ng

For many plastics recycling alternatives.

only limited data exist from which to extrapolate costs, participation rates,

technological or institutional barriers, and other factors which affect long-term

viability.

However, in order to expand the recovery and recycling of plastics and decrease the

amount of waste disposed in landfills, it will be necessary to overcome these difficulties.

Because of its heterogeneous nature and the amount of contaminants present. separation of

post-consumer mixed plastic waste is the most difficult. Waste plastics from industrial

operations are cleaner and more homogeneous in resin type and scrap form than post-

consumer plastics. The term “mixed plastics” has been used to describe broad scale

processing of post-consumer plastic waste, although no formal definition yet exists. In its

broadest sense, mixed plastics means a collection of a mixture of plastic resins or a mixture

7


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8 Mixed Plastics Recycling Technolom

of package/product types which may or may not be the same plastic type or color category,

and may not have been fabricated using the same manufacturing techniques.

While it is possible to market recycled mixed plastic waste with limited separation,

greater value and broader applications are achieved with homogeneous resins. Although it

is possible to mix different types of polymers together, the resulting physical properties are

less desirable than those of the original components. General strategies for the separation

of mixed plastics (and therefore strategies for increased recycling of plastics), with their

respective advantages and disadvantages are shown in Table 1.1. Of the live approaches

shown, three require substantial technological advances or governmental intervention (or

both): “Separation after compaction or shredding,” ”Container labeling and automated

separation” and “Standardization of resin use for certain product applications.”

Technological research regarding large scale separation of mixed plastic waste streams is

being conducted, but some of it is far from commercial application. The advances in plastic

separation technology are discussed in Part II of the book.

Governmental regulations regarding standardization for product applications and sortation

would most likely not have widespread acceptance. The remaining two approaches,

“Manual separation by consumer or collection agency” and “Collection focused on specific

resin or container type,” are currently in use. They are limited due to the cost of manual

labor and a more narrowly defined plastic type, but have the potential for application to

wider ranges of plastics than is currently collected by most recycling programs. The

purpose of this report is to identify methods used for plastics collection, plastic collection

compositions and generation rates, program costs, processing and end m,arket use of mixed

plastics in recycling. Attention is given to curbside collection of recyclables due to its high

recovery rate1 versus other collection methods [Morrow and Merriam, 19891:

B

Recovered

Curbside commingled

70-90%

Curbside home sorted 60%

Buy-back centers lo- 15%

Voluntary drop-off centers

lo-30%

‘Recovery

rate is delined as the

amount

of a recyclable disposed in a recycling collcclion conkner compared

to the total amount of a recyclable disposed by B household.


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Introduction 9

Table 1.1 Advantages and Disadvantages of Alternative Strategies to Allow Separation of

Resin Types from Mixed Recyclable Plastics @.S. EPA, 1990b]

Strategy

Separation after

compaction or

shredding

Container labeling

and automated

separation

Manual separation

by consumer or

collection agency

Advantaees

Disadvantages

Convenience to consumers;

does not require consumers to

separate wastes

Minimizes sorting, storage and

transportation requirements for

collecting agencies

Allows collection stategies

capturing large volume and

variety of MSW plastics

Convenience to consumers;

does not requite consumers

separate wastes

Promises to allow separation

into homogeneous streams

Minimizes manpower

requirements

required for sorting

Simple technology

Convenience to consumers if

collecting agency performs

separation

Allows collection strategies

capturing large volumes of

MSW plastics

Currently not possible to

separate into homogeneous

resins after shredding

Shredding yields mixed plastics

not amenable to processing into

products displacing virgin

resins

Technology not currently in

place

May require a centralized

storage and separation facility

with associated costs

Potentially prohibitive man-

power requirements

May require large storage and

transportation facilities

Inconvenience to consumers

if they are required to perform

separation


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10

Mixed Plastics Recycling Technology

Table 1.1 Advantages and Disadvantages of Alternative Strategies to Allow Separation of

Resin Types from Mixed Recyclable Plastics (Continued)

Strategy

Collection focused

on specific resin or

container types

Standardization of

resin use for

certain product

applications

Advantages

Disadvantages

Facilitates collection of

Inconvenience to consumers if

homogeneous resin streams

they are required to store and

transport recyclables to central

Allows recycling efforts to collection point

focus on high-value, high-

volume recyclable products

Captures only a small portion

of potentially recyclable plastics

Convenience to consumers

who are required to collect only

a subset of plastic wastes

Relatively low cost to recycling

agencies

Consistent with collection

strategies offering financial

incentives to recycle

Facilitates collection of

homogeneous resin streams

May imply significant

governmental intervention in

private markets

May be difficult to enlist

voluntary industry cooperation

May be applicable to only a

small percentage of recyclable

products


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Introduction 11

1 I Nati onal Product i on and Recycli ng Level s of Pl ast i cs

Plastic products are found in abundance in the homes we live in, places where we

work, clothes we wear, and the transportation we use to get about. Plastics are used to

manufacture nondurable goods* such as shoes, pens and garbage bags, durable goods3

such as refrigerators, automotive parts and computers, and packaging such as food tubs,

film wraps and bottles. The 1989 U.S. sales of all plastics (including export sales) totaled

58.2 billion pounds, with nearly all of it (92%) being U.S. domestic demand [Modem

Plastics, 19901. Of this, eight plastic types make up the majority of the annual demand

(Table 1.2). Six of the types (HDPE, LDPE, PET, PP. PS and PVC) are thermoplastics,

capable of being repeatedly softened by increases in temperature and hardened by decreases

in temperature. They are also referred to as commodity resins, meaning they are produced

in the largest volumes at the lowest cost, and have common characteristics among

producers. Polyurethane can be formed as a thermoplastic or a thermoset, the latter of

which is a resin which has undergone a chemical reaction leading to a relatively infusible

state (that cannot be reformed). Phenolics are a family of thermoset resins.

The major market destinations of plastics production are shown in Table 1.3, with a

detailed breakdown of plastic uses in the packaging industry. Consumption of the six

thermoplastics is led by the packaging industry (13,568 million pounds), accounting for

36% of the annual demand of the six thermoplastics (37,814 million pounds).

It has been estimated by the U.S. EPA [199Ob] that 29 billion pounds of plastic are

disposed in the MSW stream each year and that only 1.1% of the waste plastic stream, or

400 million pounds annually, are recovered4 (Table 1.4). Municipal solid wastes come

from residential, commercial, institutional and industrial sources, but do not include wastes

such as construction debris, household hazardous waste, or other wastes regulated by

Resource Conservation and Recovery Act Subtitle D. Seventy percent of discarded plastic

is composed of nondurable goods and packaging materials.

Similar to the EPA estimate of the annual recovery of plastics, a study for the

Plastics Recycling Foundation estimated that 340 million pounds were recycled in 1989j.

2Nondurable goods are usable only for a short period of time, a lifetime generally less than three years.

3Durable goods remain usable for a long period of time. generally products having a lifetime of more than

three years.

4”Recovery”

efers to the removal of materials from the waste stream for the purposes of recycling or

cornposting. This includes materials which may have been removed

for recycling,

but were stored,

landtilled or incinerated due to a depressed market condition.

%he primary components of recycled plastics were as follows: 160 million Ibs. PET soda botdes. 100

million Ibs. HDPE. including 40 million Ibs. of soda bottle base cups, 60 million Ibs. PP car battery

cases. 12 million Ibs. PET X-ray film and 10 million Ibs. all else [Schut. 19901.


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2


Table 1.2 1989 U.S. Consumption of Leading Plastic Resins

Abbreviation Resin Type

SPI a Code 1989 Demand b % of

Number

(million pounds) Total c

LDPE

PVC

HDPE

PP

PS

PUR

none

PETE or PET

Low Density polyethylene d 4

Polyvinyl chloride e 3

High density polyethylene 2

Polypropylene e 5

Polystyrene 6

Polyurethane none

Phenolic

none

Polyethylene terephthalate 1

Total

9,696

7,564

7,405

6,207

5,037

3,245

3,140

1.905

44,199

18.1

14.1

13.8

11.6

9.4

6.1

5.9

3.6

82.6%

.a.

b.

C

d.

e.

Society of the Plastics Industry

From Modem Plastics, 1990.

Percent of total production of all plastics.

Includes LLDPE (linear low density polyethylene - 3,286 million lbs) and EVA

(ethylene-vinyl acetate - 949 million Ibs).

Includes copolymers.

This value accounts for only 2.5% of the 1989 domestic packaging demand of the six

thermoplastics and less than 1% of all virgin thermoplastic resins. Only one specific bottle

type, PET beverage bottles, which have been targeted for recycling through curbside

collection and container deposit legislation, has reached notable recycle rates of 23% in

1988 and 28% (175 million pounds) in 1989 [Plastic News, 1990a].

Plastic resins are often difficult to distinguish from one another. Communities

performing recycling of plastic containers often train participants to identify a particular

container type (such as milk jugs) rather than the actual resin. As an initial answer to this

problem, the Society of the Plastics Industry (SPI) established a resin identification system

for the six thermoplastics for use in the packaging and container industry (see Table 1.2).

The state of Illinois passed legislation requiring the SPI resin identification code on all

plastic bottles with a capacity of 16 fluid ounces or more and all other rigid plastic

containers with a capacity of 8 fluid ounces or more that are manufactured for use in the


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Introduction 3

Table 1.3 Major Resin Markets, with Emphasis on Packaging, 1989 [Modem

Plastics, 19901

Market Category

Quantity

( lo6 lbs)

Appliances

Building

Electrical/Electronics

Furniture

Housewares

Packaging

Closures

HDPE

LDPE

PP

PS

PVC

sub-total

Coatings

HDPE

LDPE

PET

PP

PVC

Q &

sub-total

Containers

HDPE

LDPE

PET

K

PVC

W z

sub-total

Film

HDPE

LDPE

PP

F&Z

QtLI

sub-total

Packaging (total)

Toys

Transportation

1,197

11,390

2,202

1,190

1,362

81

32

420

190

2

779

51

730

10

30

21

22

1,093

3,400

311

1,049

454

1,306

352

. A6

7,018

541

3,421

612

211

310

uz

5,202

14.092

729

2,200

Major Market Total

34,362


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4


Table 1.4 Generation, Recovery and Disposal of Plastic Products, 1988 /JJ.S. EPA,

1990bJ

Product Category

MSW

Discards

(106 tons)

( lo6 tons)

Durable Goods

4.1

Nondurable Goods

Plastic plates and cups

Clothing and footwear

Disposable diapers

Other misc. nondurables

i 4

0:3

3.8

Subtotal

4.6

Containers and Packaging

Soft drink bottles

Milk bottles

Other containers

Bags and sacks

Wraps

Other plastic packaging

0.4

0.4

A.:

1:1

1.2

Subtotal

5.6

Total Plastics

14.4 0.2

1.1

14.3

< 0.1

1.5

--

0.1 21.0

-


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Introduction 15

state beginning January 1, 1991. The code is as follows: PET or PETE - 1, HDPE - 2,

PVC - 3, LDPE - 4, PP - 5, PS - 6, and all others - 7. Twenty-six other states, including

Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio and Wisconsin have also passed

legislation that requires coding by resin type for various plastic containers [Ackerman,

19901. The increased cost of landfilling waste, the volume occupied by disposed plastic

products, the value of the plastic waste material, as well as the mandate of 25% recycling of

solid waste by weight set by the state of lllinois make the addition of plastics to recycling

programs a necessity. Increasing the recycle of plastic containers, film, and packaging in

general, from the waste stream is a logical next step in increasing recycle rates.

1.2 Pl ast i cs n M unicipal Soli d Wast e

Recycling of the plastics shown in Table 1.2 has the potential for reducing the

waste stream and extending the life of landfills. Currently plastics make up an estimated

9% by weight and 20% by volume of landfill discards [U.S. EPA, 1990b], and most of it

(83%) is the six thermoplastics.

The broad identification of disposal routes and types of plastic disposed in MSW

landfills on a national basis has been performed by Franklin Associates in a study for the

Council for Solid Waste Solutions (CSWS), a program of SPI, which is supported by

major petrochemical and,polymer production companies. The study examined the disposal

routes of the 15 largest resins produced according to 1988 sales and identified which were

disposed in MSW and which were. not disposed in MSW (Table 1.5). Non MSW-

disposed wastes included industrial waste, construction and demolition debris, sludge and

incinerator residues. There is a lack of documented information regarding disposal routes

of specific plastics and therefore a substantial portion of the research was based on

communication with industry manufacturers and resin producers. The data show that for

the most part disposal of specific resins is via either MSW or non-MSW methods of

disposal (rather than both) and that PVC is the only resin of the leading six that is not

disposed predominantly through MSW. Overall, the analysis shows that 61% of plastics

are disposed in the MSW stream and 39% in the non-MSW stream. Residences were

identified as the primary source of plastics in the MSW stream, comprising 60% of the

plastics disposed, followed by the commercial sector contributing 25% and the institutional

sector contributing 15% (Table 1.6). The determination as to what plastic products could

be apportioned to the three categories of residential, commercial and institutional waste was

based on market sales information, grouping of product types, and assumptions on the pan

of the project team as to where end use of the plastic product would likely occur [Franklin

Associates, 19901.


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6 Mixed Plastics Recycling Technology

Table 1.5 U.S. Plastic Disposal, 1988 [Franklin Associates, 19901

Total Disposed

( IO6 lbs)

Non MSW Disx&

MSW 1sposal

(10; lbs) %

(lo6 lb:’ %

Pl ast i cs Di sposed Primaril y through MSW Route

ABS

1,093.3 383.1

35.0 710.2 65.0

HDPE 6J28.8 975.3

14.9 5,553.5 85.1

LDPE 7,690.8 577.2

7.5 7,113.6 92.5

PET & PBT 1,475.5 176.2

11.9 1,299.3 88.1

K 4.767.9.274.0 1,016.g

JJJ4.238.29.3 4,257.1 88.90.7

Subtotal 26,830.3 3,658.4

13.6 23,171.g 86.4

Pl ast i cs D i sposed Primari l y t hrough non M SW Rout es

Acrylic 686.0 663.3

96.7 22.7 3.3

Nylon 461.6 329.2

71.3 132.4 28.7

Phenolic 2,975.l 2,869.0

96.4 106.1 3.6

PUR 2,794.g 1,510.7

54.1 1.284.1 45.9

PVC 7,566.0 5,799.4

76.7 1,766.6 23.3

Unsat. Polyester 1,319.3 1,183.0

89.7 136.3 10.3

Urea & melamine 1.459.2

1.346.7

ubtotal 17.262.0 13.701.3

$ . 3.g z

Total 44.092.3 17,359.7

39.4 26,732.6 60.6

Table 1.6 Sources of Plastic Disposed in MSW in the U.S., 1988 [Franklin Associates,

19901

Resin

uantity

Disposed

(106 lbs)

Residential Commercial

(1061bs) % (106 lbs) %

Institutional

(IO6 lbs) %

LDPE 7.113.6 4,606.5 64.8

1,641.8 23.1 865.3 12.2

HDPE 5.553.5 3.783.3 68.1

1,007.l 18.1 763.1 13.7

K 4,257.1,238.2 2.308.0,138.6 50.24.5

1,439.gq202.5 28.43.8 678.627.5 17.25.9

PVC 1,766.6 1,033.2 58.5

347.6 19.7 385.7 21.8

PET & PBT 1,299.3 664.9 51.2

286.0 22.0 348.3 26.8

PUR 1,284.l 877.1 68.3

260.9 20.3 146.1 11.4

ABS 710.2 229.0 32.2

370.0 52.1 111.1 15.6

Unsat. Polyester 136.3 68.2 50.0

40.9 30.0 27.3 20.0

Nylon 132.4 98.4 74.3

23.6 17.8 10.5 7.9

Urea & melamine 112.5 88.3 78.5

12.5 11.1 11.7 10.4

Phenolic 106.1 63.7 60.0

32.3 30.4 10.1 9.5

Acrylic 22.7 9.1 40.1

5.7 25.1 8.0 35.2

- --

Total 26,732.6 15.968.3 59.7

6,670.8 25.0 4,093.3 15.3


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Introduction 17

I .3

Mixed Plastics in Post Consumer Recycli ng

Plastics recycling programs usually start with the simplest container/package

recognized by consumers and then move on to include additional types. In like manner,

classifying post-consumer plastic waste collection could initially begin with a few types and

expand to include additional plastic products later. In each recycling program, the

consumer/homeowner is taught differently how/what to recycle. This can lead to confusion

and inaccurate comparisons between separate recycling programs. It is important to

recognize exactly what plastic is being collected if comparisons are going to be made.

The following is a list of,plastic types collected in differing curbside recycling

ContainerPackaee ype

Colleaai

Milk jugs

(often includes water &juice)

-__-_________________

Soda bottles

--------__-__________

All #1 PET items

Beverage bottles

Detergent and bleach bottles

(often includes juice & windshield)

All #2 HDPE items

-____________________

All plastic bottles

All rigid plastic containers (RPC)

Any #l - #7 item

AlI RPCs plus W-n

(including plastic bags, film

wraps and packaging)

----------_-_________

All clean plastic products

Resins Involved

HDPE clear (unpigmented)

PET clear or green

HDPE base cup (colored)

Any container labeled with SPI 1

(An extension of soda bottle

collection)

PET (Typically fiit

HDPE 2 categories)

HDPE colored

Any container labeled with SPI 2

(An extension of milk jug and

detergent bottle collection)

PET (colored and clear), HDPE

(clear and natural), PVC, PP, and

some multilayer

PET, HDPE, PS, PVC, PP.

multilayer

Any plastic labeled with SPI 1

through 7

PET, HDPE, LDPE, PS, PVC, PP,

multilayer

Any plastic emptied of.its original

contents and rinsed


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8


While there is overlap among the above categories, the list increasingly includes

more plastic/product types from top to bottom. Near the bottom of the list, the requirement

to identify specific plastic by product type becomes less necessary.

Some recycling proms which are in the middle of the above list (e.g. detergent

and bleach bottle category, all plastic bottle category) have lengthy identilication/lnstruction

sheets for the homeowner in order to preclude collection of specific containers which arc

not blow molded (discussed in Part II) or which contain difficult to clean products

such as oil containers. The lengthy instruction requirements can lead to non-participation

because of homeowner effort and confusion. Confusion can also Icad to participants

depositing all plastics ‘gust to play it safe.” A less confusing approach would be to collect

all It1 and #2 bottles, all plastic bottles, or all RIG, since it has been shown that even a

narrowly drlined plastic stream (such as plastic beverage bottles) results in a signilicant

portion (>lO%) of the plastic deposited not being what was asked for.

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